It was 26 years ago this month Coca-Cola committed what’s regarded as one of the biggest marketing blunders of all time. But viewed through today’s lens, the New Coke debacle had little to do with product and marketing and everything to do with betrayal of the brand relationship.

First, let’s slip on our Ray Bans and look at the world of 1985.

USA for Africa eradicated world hunger and Back to the Future taught us the origin of Rock n’ Roll music. Meanwhile Pepsi was gaining the upper hand in the Cola Wars and it seemed to have something to do with the long-running and now iconic Pepsi Challenge campaign.

To address the flavor threat, Coke launched the top-secret Project Kansas. A new formula was devised and test subjects liked what they tasted. New Coke was rolled out in major markets across the Northeast and Midwest, and consumers reacted favorably to the new, markedly sweeter taste.

On April 26, 1985, coinciding with the end of production of the old Coca-Cola formula, New Coke made its official debut, and in line with spokesman Bill Cosby’s clairvoyance, consumer response was immediately positive.

But soon, grumblings that began in the Southeast gripped the nation at large, and sales for New Coke began to level off heading into the thirsty summer season. Interestingly, Pepsi was not capturing Coca-Cola drinkers, who were more content dumping out bottles of New Coke in public protest.

Coca-Cola saw the writing on the wall and flowing in the streets, and in July of 1985, barely three months after ending production of the original formula, Peter Jennings interrupted General Hospital with the news: the national nightmare would be over. Within months of the arrival of Coca-Cola Classic the new/old formula was outselling New Coke.

The Cola Wars would drag on, and not even Crystal Pepsi could turn the tide. Flash forward to April 2011: Coke is still #1 and Pepsi is now #3, ousted from its perennial #2 slot by none other than Diet Coke.

The real, 26 years-on lesson of New Coke: don’t mess with a good brand relationship.

Coca-Cola drinkers weren’t reacting to the new taste of Coke, they were reacting to every memory–real or imagined–they’d ever experienced while holding a Coke, and rebelling against the notion that Coke would desecrate those memories.

This deeply emotional–and positively irrational–brand relationship is something all of us in the branding business would kill for, and it nearly killed Coke.

And it’s for the lesson of New Coke that we make this wish to our peers who design and breathe life into brands:

May we all be successful enough to have our own New Coke moment.